A minimal binding site in 16S RNA for the S15 protein from B. stearothermophilus has been identified, which is a 65 nucleotide RNA composed of three helices that meet at a three-way junction. The 88 residue protein forms a well-behaved complex at 1 mM concentration, and the optimal temperature for well-resolved spectra is 45C. We have the capability of labeling this large complex with 13C, 15N, and 2H in a variety of different ways. We have prepared four samples 13C-labeled RNA where only one type of nucleotide is labeled with 13C in each sample. In addition, 15N labeled RNA has been prepared, and a complex with 15N-labeled protein has been made. We are in the process of recording survey spectra to obtain initial assignments for this challenging complex. We are presently implementing 2H labeling, which will be of advantage for such a large complex.